Snow-plow

ABSTRACT

Snow-ploughs for frontal mounting on road vehicles are provided with an avoidance device, which in known types can be implemented by means of two circular curved guides. This poses problems, however, during mounting as well as during avoidance, particularly on hard surfaces. In order to ensure firm and reliable mounting of the plough blade (1) on the curved guide and hence problem-free avoidance, the curved guide is designed as a sliding bearing. To this end, it comprises a first and a second curved actions. A forced limiter with a descending characteristic curve is also provided. The snow-plough is suitable for use as road snow-plough.

BACKGROUND OF THE INVENTION

The invention relates to a snow plow.

A snow plow of the general nature of the present invention is disclosedfor example, in German Published, Non-examined Patent Application DE-OS21 45 215. This snow plow has on the back of each blade two lateralcurved guides. This curved guidance is intended to assure that, when anobstacle on the ground is encountered, the respective blade is turnedout around the center of the curved guidance in respect to the obstacle,the scraping edge driving up against the obstacle first being pivotedtowards the back and then being lifted up on the curve of the circle sothat the obstacle can be overridden.

The respective blade is maintained and returned into the initialposition by a plurality of spring tension devices.

In connection with the foregoing known snow plow, a connection at only apoint or line is made because of the specific curved guidance, even ifbearing rollers are used. In case of particularly heavy snow removal,however, the forces acting on the supports are strong enough that theyresult in not inconsiderable damage and disadvantages. Moreover,problems arise in connection with the setting of the restoring force andwith the return of the blade into the operational position once it hasbeen deflected. A relatively large pivot path is traversed in the courseof the deflection movement of the blade, in the course of which thespring elements, which act on the top of the back of the blade, arestretched over a large travel of the spring. This then means that therestoring force further increases, dependent on the spring travel. Acompromise is hard to find in actual use to, on the one hand, be able toset the release forces as high as possible in case of hard removal and,on the other, not to allow the restoring forces, which further increasewith the stretching of the restoring springs, to become too great.

It is therefore the object of the present invention to overcome thedisadvantages of the state of the art and to further providing animprovement snow plow which affords increased support, and deflectionmovements without problems throughout the full range of the deflectionmovement.

A curved slide bearing is used for the first time with the snow plow ofthe present invention, which results in all-over support and forceabsorption. Because of this, and especially with heavy removal, theoccurring forces can be supported and absorbed without problems andwithout leading to an impairment of the bearing elements. Because of theadditional use of a force limiter it is possible to set the triggeringforces without problem when a ground obstacle is encountered. The forcelimiter has the further considerable advantage that after the triggeringforces have been overcome, the characteristic magnitude of force, forall practical purposes, abruptly drops down to another, preset and muchlower value in order to perform the pivot movement of the blade to theend without problem after driving up against an obstacle on the groundand overcoming the triggering force. This makes possible a safe crossingover the ground obstacle.

In a particularly preferred embodiment it is of course also possible toprovide slide bearings for the lateral support of each one of theblades.

The use of a first curved segment and a second one cooperating with ithas proven particularly advantageous. These are designed to interact inthe manner of a groove/spring connection and thus are captively guidedslidingly in respect to each other. In this way the lateral forces arealso being absorbed.

Plastics are particularly suitable as materials for the slide bearing.

In the snow plow of the invention it is possible without problems tochange and pre-set the pitch angles of the scraper edge. For thispurpose the position of the force limiter, which is supported at leastindirectly between one blade and the support frame, can be changed atleast at one connecting point, by means of which the angular position ofthe deflectable blade and thus the pitch angle of a scraper edge aredetermined. The adjustment can be performed remotely controlled eithermechanically or hydraulically, pneumatically or by an electric motor,for example by means of an eccentric, a worm, etc. Mechanical as well ashydraulic or pneumatic designs can be considered as force limiters.

In accordance with an improvement of the invention, a force limiter isused which operates not in the sense of an extension, but in the senseof a shortening when a triggering force takes effect and which for thispurpose is preferably disposed in the lower area of the blade. Itconsists of a connecting link of an elastomeric material which may be inthe shape of a strap, for example.

With an appropriate adjustment, maximum triggering forces are generatedat the start by means of this connecting link of elastomeric material,the pivoting into a deflection position only being possible when thetriggering forces are exceeded. After the triggering forces have beenexceeded, here, too, the elastomeric connecting link is beingincreasingly curved, the forces permitting further deflection of theblade are less by far than the triggering forces to be exceeded at thestart.

The direction and place of the curving operation is also determined bythe slightly arced curve in the initial position.

Thus the present invention has decisive advantages in comparison withthe already known devices. Conventional restoring springs had to be madelarge and strong. This was necessary to assuredly and quickly return theblade, which was suspended in a curved guide, from its deflection intoits scraping position after a deflection maneuver had been performed.Furthermore, it was also necessary to set the desired high triggeringforces by means of the restoring springs. Not only were the large sizerestoring springs expensive, they also have the additional disadvantagethat, when the triggering force has been attained, with increasedpivoting of the blade into the deflection position the springs arefurther stretched and thus the resilience which must be overcome in thedirection of deflection increases even more.

In contrast thereto, a force limiter is proposed by the design of theinvention where the triggering forces can essentially be setindependently of a restoring spring device and where it is also assuredin a particularly advantageous manner that, when the triggering forcehas been attained and overcome, the further adjustment movement into thedeflection position can take place without problems, because the furtheradjustment forces to be overcome after exceeding the triggering force donot increase, but diminish rapidly or are kept at a low level.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Further advantages, details and characteristics of the invention ensuefrom the following exemplary embodiments shown by means of the drawingswherein:

FIG. 1 is a schematic cross-sectional view of a blade in a loweroperating position;

FIG. 2 is a blade in accordance with FIG. 1 in its raised deflectionposition;

FIG. 3 is a schematic, excerpted cross-sectional view of a slidebearing;

FIGS. 4 and 5 are cross-sectional views of a mechanical force limiter intwo setting positions;

FIG. 6 is a schematic cross-sectional view of a blade in a loweroperating position in a changed exemplary embodiment;

FIG. 7 is a blade in accordance with FIG. 6 in its raised deflectionposition;

FIG. 8 is a schematic excerpted cross-sectional view of the energyaccumulator in the form of an elastomeric connecting link acting on thelower part of the blade; and

FIG. 9 is the setting and disposition of the lower energy accumulatorconsisting of an elastomeric material in the deflection position of theblade.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In FIGS. 1 and 2, a blade 1 with a front clearing surface 3, concave inthe direction of movement, and a lower scraper edge 5 are shown in aschematic lateral view of the snow plow. The blades 1, several as arule, are supported deflectably on a support frame 7 which, in turn, canbe suspended from the front of a motor vehicle by means of a heightadjustment, not further shown, and a subsequent holding or equipmentplate.

Between a forward linking point 9 on the back of a blade and a rearlinking point 11 on the support frame 7, at least one force limiter 13and a restoring device 14, for example in the shape of a spring whichacts between the frame and the blade, for each blade 1 is mounted, whichcan be adjusted in position preferably via an adjusting device 15. It ispossible to pre-set a pitch angle 17 of the scraper edge 5 in respect tothe vertical of the plane of the road by means of extending orshortening the adjusting device 15.

As can be seen from the drawings, each blade 1 is deflectably held onthe support frame via a curved guide 19. For this purpose a curved guide19 is disposed on the back of each blade, preferably at its lateraledge, which consists of a first and second curved segment. The radius ofthe curved guide 19, i.e. the first and second curved segment 21 and 23,is less in the exemplary embodiment shown than the lower, changingcurved radius of the clearing surface 3. Moreover, the radius of thecurved guide 19 has been selected such that the associated center 25 islocated at the height of or in front of the contact straight line of thescraper edge 5 on the surface. In this way it is assured that in thecourse of encountering a ground obstacle the respective blade 1 does notpress down on the surface, but is immediately lifted simultaneously withbackward pivoting above the curved guide in order to avoid the groundobstacle in this way, as is illustrated in a second deflection positionin FIG. 2.

It can be seen from the cross-sectional illustration of FIG. 3, that arib 27 extending to the back is provided in the vertical lateral area onthe back of a blade 1, on which the one first curved guide 21,consisting of two parts, is fixed by means of screws 29. The secondcurved guide 23 is fixed on the support frame 7 via a support member 31by means of screws 29'. The two curved sections 21 and 23 are captivelyguided, interlockingly, via spring/groove catches 33 which are in theshape of an arc of a circle. Plastic with low friction and high slidingability is particularly suitable as a material, such as polyethylene,particularly with a high polymerization degree.

Based on the described structure it is immediately clear that it ispossible, when encountering a ground obstacle, that the forces directedto the blade are absorbed over the full width of the curved slidingsurface 35 between the first and second curved section 21 and 23, sothat damage and impairment of this slide bearing is impossible for allpractical purposes. Furthermore, by means of the spring/groove catch 33,laterally acting forces are absorbed and supported, for which reason aplurality of blades guided next to each other are guided with extremeexactitude, so that lateral deflection is completely avoided for allpractical purposes. It is also possible to provide an upper and lowerstop for safety's sake, by means of which the maximum curved deflectionis limited.

A mechanically operating force limiter 13 will be described in detailwith respect to FIGS. 4 and 5.

It can be seen from these drawings figures that a rod 37 is connectedwith a housing 41 via locking elements 39. The locking elements 39 arepressed via the disk spring assembly 43 into a groove 45 of the rod 37and against conical surfaces 47 formed on the housing 3. If a force isacting between the rod and the housing, no movement takes place betweenthe two parts until the triggering force is attained. If the force isincreased, the rod 37 moves in relation to the housing 41, so that thetotal distance between the two linking points 9 and 11 is increased andin this way the blade 1 can be pivoted counterclockwise around thecenter 25 of the curved guide 19. Immediately after exceeding thetriggering force, however, the force acting and required in the forcelimiter 13 for further longitudinal changes immediately drops to a muchsmaller, adjustable value.

The triggering force can be easily set by a change in the amount ofdisks 49 for the disk spring assembly 43. Although the energyaccumulator shown operates in both directions (and here with variedtriggering forces), it is possible to use in the present exemplaryembodiment a unilaterally acting force limiter.

Thus, use of the force limiter makes heavy removal possible, because itis possible to set optionally high triggering forces and the snow plowblade is not deflected until they have been reached. After exceeding thetriggering force, however, the characteristic curve in the force limiter13 drops so clearly that it is possible to pivot the blade away from theground with small force up to its maximum, final position. Reversepivoting takes place by means of a restoring device 14 which mayconsist, for example, of a relatively small-sized restoring spring.

As explained, the adjustment angle 17 can be pre-set by a device whichis schematically illustrated as adjusting device 15. This can be done,for example, by moving the rear or front linking point 9 or 11 toanother bore between the force limiter 13 via a manually operated boltsupport. However, a motorized, electrical, pneumatic or hydraulicadjustment is also possible in order to be able to set any optionalpitch angle, for example, from the cab. This can take place, forexample, via an eccentric or a motor-driven worn, in order to optionallybe able to set the distance between the linking points 9 and 11, or theposition of a linking point, and thus the pitch angle 17.

A changed exemplary embodiment will be described below by means of FIGS.6 to 9, like parts having the same reference numerals. The exemplaryembodiment described below differs from the exemplary embodimentexplained above in that, in place of an upper energy accumulator orforce limiter 13, a lower energy accumulator or limiter 13 is used,which is comprised by a lower elastomeric connecting member 13'.

This connecting member 13', shown in FIGS. 8 and 9, is clamped by meansof screws 59 at a forward end directly on the lower edge of the blade onan angle iron 51 on the back of the blade to a fastening means 53disposed there between an abutment surface 55 and a support rail 57. Inother words, the end of the connecting member 13' made of an elastomericmaterial is clamped sandwich-like between the abutment surface 55 andthe support rail 57, the screws 59 extending through the correspondingbores through this sandwich construction. At the front the support isachieved by means of the rearward extending leg 61 of the angle iron 51.

The alignment of the abutment surface 55 takes place almost tangentiallyto the corresponding curved section of the front blade. In the exemplaryembodiment shown, the angle deviates by 5° from the lower tangent of theblade curvature. Angles from 0° to 20°, preferably 2° to 15° or 10°,mainly around 4° to 6°, are very suitable.

A support and a bearing device 63 is also provided for the back end ofthe connecting members made of an elastomeric material which comprisesan angular rail 65 and an opposite rail 67, which again sandwich-likesurround the connecting member 13' between them and support the frontend of the connecting member with the one obliquely extending leg of theangular rail 65. Again, fastening is accomplished by means of screwsextending crosswise through the entire device and which are not furthershown in the exemplary embodiment illustrated.

In contrast to the forward support and bearing device 54, the rearsupport and bearing device 63 provided on the respective support frame 7is flexibly suspended by means of a hinge pin 69 on the support frame 7.

In the plowing position the elastic energy accumulator 13' in the shapeof an elastomeric connecting member takes up the slightly curvedpre-stressed basic position shown in a cross-sectional view in FIG. 8.The curvature and curved position in the deflection position is set bythe slight curved pre-stressing with the convex curvature in thedirection towards the back of the blade.

The triggering force is determined by means of the at least almosttangential positioning and corresponding to the selected material anddependent on the geometric shape of the connecting member 13'. Onlyafter exceeding the triggering force, however, the characterizing powerline immediately drops, so that further pivoting then can take placewithout problems, the end position of the energy accumulator 13'comprised of an elastomeric material being mainly shown in FIG. 5.

The restoring spring 14 shown in FIGS. 6 and 7 can be set or selected inits base position with only slight pre-stressing, because in theembodiment shown this restoring spring 14 only has the function ofreturning the blade from the deflected position into the plowingposition. In other words, the restoring spring 14 does not have thefunction of the only or supplemental "triggering energy accumulator,"because this would have the disadvantage that springs with highpre-stressing forces would have to be selected which would maintain theblade in the pre-stressed plowing position by means of correspondinglyhigh force.

This, then, during pivoting into the deflection position, would have thefurther disadvantage that with added tension of the restoring spring itsrestoring force would further increase, which is exactly what isintended to be avoided.

As a rule, at least one elastic connecting member 13' per deflectableblade is used on the left and right edges respectively.

To be complete, it should be mentioned that basically not onlymechanically operating, but for example pneumatically or hydraulicallyoperating force limiters 13 are possible and conceivable. A pressuresensor would be required for this, by means of which the forceintroduced via the scraper edge are measured and, when a limit value hasbeen exceeded, the pressure in a pneumatic or hydraulic piston, actingas force limiter, would be suddenly released in such a way that adeflecting movement becomes possible. The pressure sensor might beassociated, for example, with the pressure chamber of a hydraulically orpneumatically operating force limiting piston in order to be able tomeasure the introduced plowing forces and to relieve the force limitingpiston suddenly. Mechanically operating force limiters, however, arepreferred over hydraulically operating force limiting pistons 13,because the latter are slower to change by reason of the inertia of thehydraulic medium.

What is claimed is:
 1. A snow plow for a vehicle comprising:a snow plowblade; a support frame for securement to the vehicle; means forconnecting said blade and said support frame one to the other enablingpivotal deflection of the blade in one direction relative to saidsupport frame and about an axis upon the blade encountering a groundobstacle; said connecting means including a pair of generally curvedguides on said blade and said support frame defining generally curved,elongated contact surfaces, respectively, relatively slidable about saidaxis with substantially the entirety of one of said curved elongatedcontact surface lying in engagement with the other of said curvedelongated contact surface throughout the full range of deflection ofsaid blade relative to said support frame about said axis; and a forcelimiter disposed between said blade and said support frame forpreventing substantial deflection of the blade relative to the supportframe in response to a force, up to and including a predeterminedmagnitude of force, applied to said blade by the ground obstacle,tending to deflect the blade in said one direction, said force limiterenabling deflection of said blade in said one direction in response to aforce applied to said blade in excess of said predetermined magnitude offorce and including means enabling deflection of said blade in said onedirection, after exceeding said predetermined magnitude of force, inresponse to an applied force less than said predetermined magnitude offorce.
 2. A snow plow according to claim 1 wherein said curved guidescomprise a slide bearing supporting the blade against movement in alateral direction.
 3. A snow plow according to claim 1 wherein saidcurved guides include cooperating flanges and grooves extending in adirection generally parallel to said axis, enabling said blade and saidsupport frame for captive guided movement relative to one another aboutsaid axis.
 4. A snow plow according to claim 3 wherein said bladeincludes a pair of ribs extending from a back side thereof and carryinga first pair of said guide surfaces, a second pair of said guidesurfaces being carried by said support frame.
 5. A snow plow accordingto claim 1 wherein said contact surfaces are formed of plastic materialhaving a low friction coefficient.
 6. A snow plow according to claim 5wherein said plastic material comprises polyethylene.
 7. A snow plowaccording to claim 1 including means for displacing said blade relativeto said support frame in a second direction opposite said one direction.8. A snow plow according to claim 1 including means carried by saidforce limiter for enabling setting of the pitch angle of said bladerelative to said support frame.
 9. A snow plow according to claim 1including means carried by opposite ends of said force limiterengageable with said blade and said support frame, respectively,enabling a change in the effective length of said force limiter toaccommodate variable pitch angles of said blade relative to said supportframe.
 10. A snow plow according to claim 1 wherein said force limiterincludes a connecting member formed of an elastomeric materialdeformable out of a generally longitudinally extending initial shape ina plowing position of the blade into a deformed curved shape in adeflected position of the blade.
 11. A snow plow according to claim 10wherein said elastomeric connecting member is connected at one end tosaid blade below the axis of rotation of the curved guides.
 12. A snowplow according to claim 11 wherein said elastomeric connecting member isconnected at its opposite end to the lower end of the blade.
 13. A snowplow according to claim 10 wherein said blade is curved, saidelastomeric member is connected at its opposite ends to said blade andsaid support frame and in said plowing position lies substantiallytangentially to the curved shape of said blade.
 14. A snow plowaccording to claim 13 wherein the connection between one end of theelastomeric member and said support frame includes a bearing pivotallycoupled to said support frame.
 15. A snow plow according to claim 13wherein said elastomeric member, in the plowing position, is elongatedand curved.